Arrangement for acoustic cinematography



J. MASSOLLE ET AL ARRANGEMENT FOR ACOUSTIC CINEMATOGRAPHY f ct 20,1925. 1,558,032

Filed April 4. 1921 MICROPHONE FILM STAGE GREEN vwemtozi /5 Mmsi 41/4 Patented Oct. 20, 1925.

- UNITED STATES 1,558,032 PATENT OFFICE.

:rosnrn mAssoLLE', or GRUNEWALD, HANS voo'r', or maLrn-sononnnm, AND JOSEF ENGL, or GRUNEWALD, GERMANY, ASSIGNORS 'ro TRI-ERGON LIMITED, or

? ZURICH, SWITZERLAND.

I ARRANGEMENT r'on noousrrc GINEMATOGRAPH'Y.

Application filed April 4, 1921. Serial No. 458,629..

To all whom it may concern: I

Be it known that we, JOSEPH MASSOLLE, HANS V061, and Josnr Ensncitizens of the German Republic, residing at Grunewald, I Berlin-Schoneberg, Grunewald, Germany, respectively, have invented certain new and useful Improvements in Arrangements for Acoustic Cinematography (for which We have filed an application in Germany July 1 25, 1919), of which the following is a specification.

In acoustic cinematography the optical operation is photographically recorded upon a film in parallel with the acoustical opera- 1 tion in order to ensure synchronism. For

the reproductiom positives made from thesenegative records'are converted by means of photoelectric 'cells into micro currents of acoustic characteristicsythat is to say, light is passed through the positive sound record on the film, and falls on the cell, which produces the currents. For recording, the current produced by a microphone is fed to a recording lamp, the varying illumination of which produces a photographic record'upon the negative film. -The microphone, in recording, and. the photo-electric cell in reproducing, each constitute a means for producing anacoustically-modulated current.- These known arrangements have however important disadvantages. In particular the microcurrents (of the order of magnitude 10". to 10" amperes) are not sufficient to uniformly reproduce with sufficient volume the sounds produced by them in. a room of considerable size. The use of low frequency amplifiers has the disadvantage that in accordance with prior practice low frequency transformers have to be used as a coupling means which in consequence of magnetic hysteresis, undesirable resonance positions and the capability of taking up disturbing low frequencyalternating fields, cause falsification of the speech and of its tone colour and intensify further also all disturbing noises. Very strong electro-magnetic disturbing fields manifest themselves in cinematographic apparatus, the i inductive action of which is especially marked on the amplilamp of the moving picture projecting ma fier circuits of the acoustic apparatus, if

chine, (closely adjacent to the acoustic apparatus), by the motor for the projecting.

'machine, by the electric lamps by which the stage is lighted in recording, etc. These cause the disturbing effects on the low frequency transformers, as notedabove.

In consequence hereof thesemethods of intensification have hitherto not obtained any practical importance. The effect of the synchronism between the optical and acoustical operation may be annulled by adistorted reproduction of the speech or other sounds, particularly when an amplification of this speechor sound andwith it an augmentation of its distortion-is necessary.

This invention has for its object an arrangement which enables amplification to be produced free from distortion without the above described disadvantages. This arrangement avoids all the hitherto customary agencies, which together with sources of disturbance, such as those mentioned prevent the distortion free recording and reproduction of the acoustic operations. k

The invention consists accordingly in the use, (-in'acoustic recording and reproducing systems embodying amplifiers, which systems are used in connection with moving picture recording and re roducing apparatus 'in-which sources 0 disturbance are present, such for example, as those mentioned), of coupling. means for various of the elements of the acoustic system, by which the-effect of such disturbances on'the amplifier circuits will be prevented.

The arrangement consists in the combination of the recording and reproducing means, (microphone, photo cells, telephone,

etc.) with amplifiers (,vacuum tubes) which possess no inertia, and whose elements are galvanically coupled, i. e. resistance-coupled, without the use of low frequency transformers. The arrangement may also be carried out in such a manner that for the purpose of influencing high frequency currents by acoustic currents high frequency amplifiers without inertia are used with iron free high frequency transformers as coupling means therefor. These high-frequency transance by low-frequency magnetic fields, such as those produced by the sources of disturbance mentioned. In this arrangement a high frequency alternating current of conformers are relatively insensitive to disturbampli er 8, it being understood that as many amplifiers are used in this system as isfound desirable. From-the last amplifier of a 6 the series, illustrated as the amplifier .8 an

stant frequency is transmitted from one amplifying tube to the next, the amplitudes thereof being of various magnitudes according to the acoustic influence; that is to say, high frequency current from a suitable alternating current source is fed into the system, and this is modulated acoustically; The disturbances and distortions which are caused by low frequency transformers are consequently avoided in the new arrangement. In the present application the species of invention first referred to, involving the use of the resistance couplings, will not be specifically claimed, the same being covered in a divisional application, Serial No. 746,741 filed'Oct. 29, 1924. The freedom from disturbance c'an in the second form of arrangement described also be further increased by the use of. resonance circuits.

The invention is exemplified in the appended drawings,"in which Fig. .1 represents diagrammatically a system for simultaneously recording, on a'moving film, pictures and the accompanying sounds, the resistancemoving picture apparatus 3, pictures thus being made for example of actors upon a. stage 4 illuminated in the usual way by arc lamps,"

" whichare indicated at 5----5.

The speech or'other sounds produced b y the actors or accompanying their action fall upon a microphone indicated diagramaticrophone, which current is Sound-modulated,-

cally at 6. A current is accordingly'pro-- duced in the circuit 7, leading from the mithat is it fluctuates in correspondence with the sound producing the same. This circuit leadsito a thermionic amplifier 8, one side of "'the'circuit being connected to the usual fila;

, ment 9 of the amplifier and the other side to the grid 10, in the usual manner. Amplified current flows from the plate 11 of am lifier 8 to the grid 10 of a second output circuit 12 is indicated as leading to a recording lamp indicated diagrammatically at 13. The illumination of this lamp is varied in accordance with the sound modulated current received thereby and the light thus varied falls upon the film 1 to make a mam negative record corresponding to the sound as is Well-known. The amplifiers of the system are coupled together by resistances, re- I sistance ,15 being indicated as connected across the output circuit of amplifier 8 in the Well-known manner. Similarly the microphone 6 is illustrated as resistance coupled to the first amplifier 8, resistance 15 being shown as connected acrbss the circuit lead-. ing from'the microphone to the filament and grid of the tube 8. Batteries, 16, 16 and 16 are conventionally indicated as included in the circuits 7, 17 between the amplifiers, and

12 extending between amplifier-8 and the recording lamp-13, this being, of-course, c0n1- mon practice. A resistance-15 is also indicated as included in the circuit 12 leading from the last amplifier. Condensers 18 and 18f are indicated in the grid leads of amplifiers 8 and 8 merely by wayof example. It ma'yrbe noted that coupling resistance 15 for the microphone corresponds to the resistance described in our copending application Serial No. 458,632, entitled Method for the control of electric currents by power of sounds, filed April 4, 1921, and there stated 6 to be the coupling resistance of the micro-- phone for amplifying or intensifying tubes. In Fig. 2, illustrating the high'frequency transformer coupling form of the invention,

' the invention is indicated by Way of example as applied to a sound reproducing system accompanying moving picture projection appa ratus;

In Fig.2v the film 1, bearing the .pictures,

and also the sound record is fed past the T projection-lamp 19, which may be a powerful arc lamp, the light from which passes through the picture record on the fihn and is projected on screen 22 in the usual manner. This lamp is a. source of considerable electro-magnetic disturbance for adjacent electrical apparatus, such as the acoustic apparatus close by.

Light from a source 23 passes through the sound record on the film and falls upon the photo-cell, such as the photo-electric cell 24.

The circuit 25 leading from this cell connects to the vacuum tube amplifier 26, the

-anode 24 of the cell being'illustrated as connected to the grid 26 of the tube, and the cathode 24 'of the cell to the filament 26*of the tube. The output circuit of tube-26 is connected to the grid and filament of a second tube 28 by'a highfrequency, iron-free, air-cbre transformer-coupling 29. As many tubes connected together by'similar transformer couplings asflare desired may be used. 'From the last tube appropriate conbe made to a suitable telephone or loud speaker (not shown). High frequency A. C. current may beintroduced into the system from a suitable source for example by the transformer coupling indicated at 30.

nection' as by transformer coupling 29 may aasaosa i The connections indicated are the usual ones for transformer-coupled amplifying apparatus; The transformer circuits may tuned, if desired, by the use of suitable condensers (not shown), as .is well-known, to

produce the resonance circuits referred to.

I A resistance 27 is indicated as connected in the anode-cathode circuit of the photo-cell 24.

The species of invention involving the high frequency transformer couplings may, as stated, be used in a'recording system as well as ina reproducing system, in which case a microphohe would be used in place system.

We claim: J I 1. In acoustic-cinematographic apparatus, including an electric device adapted to cause electro-magnetic disturbances in adjacent electrical ap 'aratus, the combina-.

tion of means for pro ucing an acoustically? modulated electric current, thermionic amphfymg means and coupling means betweencoupling various of said means constructed to prevent the disturbing efi'ect of said. device in the circuit of said amplifying means; acoustic-cinematographic appa- 2. In ratus, including an electric device adapted to cause electro-magnetic disturbances .in ad- 1 of means for producing an acoustlcallymodulated electric current, a plurality of amplifying tubes, connections between said first' named means and thefirst tube and means between successive tubes comprising high-frequency air-core transformers, and. connections. for transmitting high-frequency alternating current to the input circuitof said first tube.

3; -In acoustic-cinematographic to' cause electro-magnetic disturbances in adjacent electrical ap aratus, the combination of means for pro ucing an-acoustic'allythergmomc modulated electric current, amplifylng means and coupling means between all of said means constructed to acent'electrical apparatus, the combination ur ratus, including an electric device adapted a prevent the disturbing effect of said device in the circuit of said amplifying means.

Intestimony whereof we afiix our signatures.

HANS VOGT. DR. JOSEF ENGL.

. JOSEPH ismssonnn. 

